The animal rights activist who gunned down the Dutch prime ministerial candidate Pim Fortuyn last year said at the start of his trial today that he committed the crime to protect the country's Muslim minority from Fortuyn's anti-immigration policies.

Volkert van der Graaf, 33, was arrested minutes after Fortuyn was shot dead in a parking lot outside a radio studio on May 6, 2002, just days before general elections.

Mr van der Graaf was caught with the murder weapon in his pocket and spatters of Fortuyn's blood on his pants. In November, he admitted the murder.

In court today, Mr van der Graaf openly answered questions about the motives behind the first political assassination in modern Dutch history. Although he has confessed, under Dutch law prosecutors need to present their case to a panel of judges. There are no jury trials in the Netherlands.

Wearing a purple shirt and khakis, Mr van der Graaf walked into the courtroom looking relaxed and confident. He briefly scanned the public gallery for familiar faces, avoiding eye contact with Fortuyn's two brothers, Marten and Simon, sitting just a few yards away.

"(The idea) was never concrete until the last moment, the day before the attack," he said. "I confess to the shooting."

He also confessed to illegal possession of firearms and to sending Fortuyn threats before carrying out the attack. Mr van der Graaf said he had followed Fortuyn's career as a columnist for a popular national magazine and had was concerned he was using "the weak parts of society to score points" and gain political power.

Muslims in the Netherlands were being used as "scapegoats", he said. "I saw it as a danger, but what should you do about it?" he said "I hoped that I could solve it myself."

Separated from the courtroom by a bulletproof glass barrier, onlookers continuously interrupted the proceedings, denouncing Mr Van der Graaf as a murderer and chanting "Life! Life!" to press for a tough sentence.

One woman stood up to demand Mr Van der Graaf be jailed for the rest of his days, saying he "devastated the country", before being dragged away by bailiffs to join a handful of Fortuyn supporters outside. He is charged with premeditated murder and faces a maximum life sentence if convicted. During several days of hearings at a high-security courtroom nicknamed "the bunker" judges will consider his mental state at the time of the shooting and whether he can be held accountable for his actions.

Fortuyn, a brash gay academic, swiftly gained popularity with calls to close the borders to newcomers, at one time dismissing Islam as a "backward religion". His party won more than 10% of the vote and a place in the three-party rightwing governing coalition.

After its unprecedented rise in power, bickering in Fortuyn's party led to the fall of the government and fresh elections in January. With coalition talks ongoing, political stability has yet to return to the country. A graduate of the country's leading agriculture university, Mr van der Graaf went on to become a tough and successful litigator against commercial animal farming. At the time of the murder, he lived with his longtime girlfriend and baby daughter.

In prison, he went on hunger strike for more than two months to protest around-the-clock camera surveillance in his cell.

Mr van der Graaf remains the only suspect in the case, although prosecutors never ruled out that he may have worked with others. In raids of the couple's home, police investigators recovered chemicals needed to make explosives and bullets that matched those found at the crime scene.